[WIP] Feature/csv to sql natively

When finished, this PR should address #352. New `into` function calls out to to native COPY function of various DBs.  Has optional `if_exists` argument (similar to pandas) to handle three cases: replace, append, and fail

```python
into(sql,csv, if_exists="replace")
```


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Agreed!  When I nail down postgres and sqlite I'll look into windows functionality before moving onto MongoDB with [mongoimport](http://docs.mongodb.org/manual/reference/program/mongoimport/)